1. Field of the Invention
The present invention relates to a disc device for rotatably holding a disc, such as a compact disc (CD) or a digital video disc (DVD), or a disc used in, for example, a compact disc read only memory (CD-ROM). More particularly, the present invention relates to a disc device which makes it possible to reduce a load on a mechanical part and which can reliably clamp a disc.
2. Description of the Related Art
FIGS. 14A and 14B are side views of the main portion of a conventional vehicle-mounted disc device. FIG. 14A shows an unclamped state of a disc, while FIG. 14B shows a clamped state of the disc.
In the disc device, a slit-like insertion slot 2 is formed in a face provided at the front surface of a housing 1. A disc D is inserted into the housing 1 from the insertion slot 2. A transfer roller 4 and a roller supporting member 3 for supporting the transfer roller 4 are provided inwardly of the insertion slot 2. A guide member 5 is provided above the transfer roller 4.
A supporting base 6 that is supported in an elastically raised state by, for example, a clamper is provided inside the housing 1. A spindle motor M and a turntable T, rotationally driven by the spindle motor M, are provided on the supporting base 6. In addition, an optical head (not shown) and other component parts are provided on the supporting base 6. A clamping member 7 is rotatably supported on the supporting base 6 through a supporting shaft 9. A clamper 8 for clamping a disc D on the turntable T as a result of pushing the disc D is rotatably supported at an end of the clamping member 7. A coil spring 10 for urging the clamping member 7 in the direction of the turntable T is provided near the supporting shaft 9.
In FIG. 14A, the clamping member 7 is lifted by an unclamping member (not shown), so that there is a gap between the turntable T and the clamper 8. When the disc D is inserted from the insertion slot 2, the disc D that is clamped by the transfer roller 4 and the guide member 5 is transferred into the gap between the turntable T and the clamper 8. When the center of the disc D and the center of the turntable T coincide, a lifting force of the unclamping member on the clamping member 7 is removed. At this time, because of the elastic force of the coil spring 10, the clamping member 7 is rotated in the clockwise direction upon the supporting shaft 9 as a fulcrum, in order to, as shown in FIG. 14B, cause the clamper 8 to push the center portion of the disc D against the turntable T and to clamp the disc D.
Then, the spindle motor M rotates to rotationally drive the disc D by the turntable T, so that a signal recorded on the disc D is read by an optical head (not shown).
In the conventional disc device shown in FIG. 14, a moment Mc in the clockwise direction is applied to the clamping member 7 by the coil spring 10, so that, because of the moment Mc, a clamping force Fc for clamping the disc D is exerted on the clamper 8. Here, when the point upon which an elastic force f applied to the clamping member 7 from the coil spring 10 acts is expressed as 10a, and the distance from the center of the supporting shaft 9 to the elastic force f acting point 10a is expressed as L1, the moment Mc is equal to L1xc3x97f. In the clamped state shown in FIG. 14B, when the point upon which a clamping force Fc applied to the clamper 8 by the clamping member 7 acts is expressed as 7a, and a distance from the center of the supporting shaft 9 to the force acting point 7a is expressed as L2, Fc=(L1/L2)xc3x97f.
Therefore, the elastic force f of the coil spring 10 must be larger than the clamping force Fc required to clamp the disc D by the clamper 8 by a factor of L2/L1.
For example, in the case where, in order to clamp the disc D, a clamping force Fc of 3 N (approximately 306 gf) with respect to the clamper 8 is required, when L2/L1=4, the coil spring 10 needs to provide an elastic force f of 12 N (approximately 1.22 kgf).
When a coil spring 10 with such a large elastic force f is used, a large force is applied to the base of the clamping member 7 from the coil spring 10, so that a distortion tends to occur at the base of the clamping member 7. In addition, a large load also acts upon the portion of the clamping member 7 rotatably supported by the supporting shaft 9.
In the conventional structure, when the state of the disc D is to be changed to the unclamped state shown in FIG. 14A, the clamping member 7 is lifted by the unclamping member. Hitherto, a point upon which a lifting force Fu, applied to the clamping member 7 from the unclamping member, acts is set at the base end portion side of the clamping member 7. Accordingly, when the disc device is constructed so that the clamping member 7 is lifted obliquely upward with the supporting shaft 9 as a fulcrum, the distance that the clamping member 7 is lifted by the unclamping member can be made small by lifting the base end portion of the clamping member 7.
However, when the disc device is constructed so that the lifting force Fu is applied to the base of the clamping member 7, since the distance between the lifting force Fu acting point and the center of the supporting shaft 9 is small, a very large lifting force Fu is required. In general, the unclamping member comprises a cam plate that moves towards the left and right in FIGS. 14A and 14B, and lifts the clamping member 7 by an inclined groove formed in the cam plate. However, since a large lifting force Fu is required, a large driving force is required to move the cam plate. Therefore, a large frictional force acts between the cam plate and the clamping member 7, so that rattling and wearing at a sliding portion between the cam plate and the clamping member 7 tend to increase.
In order to overcome the above-described problems in a conventional device, it is an object of the present invention to provide a disc device, in which, even when a biasing member having a weak elastic force for applying a clamping force to a clamping member is used, a disc can be reliably clamped; in which, by a biasing force of the biasing member, distortion or wearing by driving does not easily occur in a mechanical component part; and in which a force required to unclamp the disc can be made small.
To this end, according to a basic form of the present invention, there is provided a disc device comprising a turntable for placing a center hole of a disc thereon, a clamper for clamping the disc along on the turntable, a clamping member including a clamping force acting portion for exerting upon the clamper a force for clamping the disc, a supporting portion for supporting the clamping member, and a clamping elastic member for producing a disc clamping moment having the supporting portion as a fulcrum with respect to the clamping member by action on the clamping member at a location separated from the supporting portion. In the disc device, the distance from the supporting portion to a biasing force acting portion upon which a biasing force of the clamping elastic portion acts is greater than the distance from the supporting portion to the clamping force acting portion.
In the present invention, by setting the positional relationship among the clamping portion supporting fulcrum of the supporting portion, the clamping force acting portion, and the biasing force acting portion as mentioned above, the clamping elastic member used may be one with a weak elastic force, so that it is possible to prevent a large localized force from acting on, for example, the clamping member.
When the structure of the basic form is used, the disc clamping moment may act directly on the clamping member from the clamping elastic member. Alternatively, when the structure of the basic form is used, the disc device may further comprise an intermediate member for being subjected to an elastic force from the clamping elastic member, in which the disc clamping moment acts on the clamping member through the intermediate member.
When the disc device further comprises an intermediate member for being subjected to an elastic force from the clamping elastic member, in which the disc clamping moment acts on the clamping member through the intermediate member, the disc device may further comprise unclamping means for moving the clamping member against the disc clamping moment in a direction in which the clamping member moves away from the turntable.
Here, by the action of the unclamping means, the clamping member may be lifted away from the turntable while the clamping member is kept in a posture parallel to the chassis at which the turntable is provided, or may be lifted so as to rotate with the supporting portion as a fulcrum.
When the disc device further comprises unclamping means for moving the clamping member against the disc clamping moment in a direction in which the clamping member moves away from the turntable, the disc device may further comprise a holding elastic member for biasing the clamping member towards the turntable at a supporting portion side.
When the holding elastic member is provided, the position of the supporting portion, serving as a fulcrum of the clamping member, can be stabilized.
When the disc device further comprises a holding elastic member for biasing the clamping member towards the turntable at a supporting portion side, the supporting portion may be provided at a chassis for supporting the turntable, and, by an elastic force of the holding elastic member, the clamping member may be biased so as to come into contact with the supporting portion.
When the disc device further comprises unclamping means for moving the clamping member against the disc clamping moment in a direction in which the clamping member moves away from the turntable, the supporting portion may protrude from the clamping member, a driving member for moving the supporting portion against the disc clamping moment in a direction in which the supporting portion moves away from the turntable may be provided at the unclamping means, and a portion where the supporting portion and the driving member engage may be a fulcrum for the disc clamping moment.
When the supporting portion protrudes from the clamping member, a driving member for moving the supporting portion against the disc clamping moment in a direction in which the supporting portion moves away from the turntable is provided at the unclamping means, and a portion where the supporting portion and the driving member engage is a fulcrum for the disc clamping moment, the disc device may further comprise a holding elastic member for biasing the supporting portion towards the turntable by biasing the driving member.
When the disc device further comprises unclamping means for moving the clamping member against the disc clamping moment in a direction in which the clamping member moves away from the turntable, the unclamping means for applying an unclamping force to the clamping member in the direction in which the clamping member moves away from the turntable may be provided at a side where the biasing force of the clamping elastic member acts, and a distance from the supporting portion to an unclamping force acting portion upon which the unclamping force exerted upon the clamping member from the unclamping means acts may be greater than the distance from the supporting portion to the clamping force acting portion.
When the disc device has this structure, the driving force of the driving member for moving the clamping member away from the turntable can be made small, thereby making it possible to reduce a drive load and to prevent excessive wear between mechanical parts.
When the disc device further comprises unclamping means for moving the clamping member against the disc clamping moment in a direction in which the clamping member moves away from the turntable, the disc device may further comprise a chassis having the turntable mounted thereto and being elastically raised and supported, and the unclamping means may include a lock portion for causing the chassis to be in a locked state when the clamping member is moved in the direction in which the clamping member moves away from the turntable. Alternatively, when the disc device further comprises unclamping means for moving the clamping member against the disc clamping moment in a direction in which the clamping member moves away from the turntable, the disc device may further comprise a transfer roller, disposed between the turntable and the clamper, for bringing in the disc, and the unclamping means may include a roller position controlling portion for moving the transfer roller away from a disc transfer position when the clamping member is moved towards the turntable.
Using the unclamping means, by locking and unlocking the chassis and by controlling the position of the transfer roller, a driving mechanism can be used in common, thereby simplifying the mechanism.